Is this a bug? When i send this message it appears fine in the Sent folder... and i tried to send messages for myself and in thunderbird it looks allright too. But i send to my wife that she use Evolution mail and it shows with the strange characters. The same characters that Thunderbird shows when it is signing the message.

I can confirm the bug is in Enigmail, because sending the same message without signing, the character encoding is the correct one. Also i confirmed that Evolution is not mis-reading the mail. I sent a mail from k-9 mail client from my android ICS tablet signed with the same private key and Evolution reads the message fine.

In Evolution, btw, the message footer says "Key is not Valid" and my wife kave my public key in seahorse, that confirms that Enigmail is messing up with the keys. The same signed message sent from k-9 says "Key Valid" in the message footer.

Ok, i solved the issue going to Edit > Preferences > Display: under Fonts > Advanced and there was Western ISO .. and UTF-8 encodings in outgoing and incoming. The issue still in the sense that you actually can set up UTF-8 encoding when composing messages and when hit send, Thunderbird changes the encoding to Western and the spanish tildes go bananas and the PGP sign gives a different hash that the one that was calculated in UTF-8 ebcoding. This is still an issue because when you change encoding for a particular message, the above setting overrides it and messes up with the PGP sign validity.